? How can i make the LEDs work?

rustcoal132 · Post by **rustcoal132** » Sat Jun 11, 2005 11:08 am

i got one in the modem, and five (including the main LED) using the 3.3v on the powersupply. when i add another LED, they all turn off, i guess its because lack of power, what should i do?

dcmodder · Post by **dcmodder** » Sat Jun 11, 2005 4:44 pm

where (exactly) are you taking the power from. the actual psu (power source unit) or the pins that come from the mother board.
if you're not running the leds in parrelel form one of the "dead" leds could be stopping the current to the others. kind of like (certain) cristmas light strands. if one's out they're all out.

doragasu · Post by **doragasu** » Sat Jun 11, 2005 5:54 pm

Each LED needs to have the right polarization, and needs some voltage to work, it depens on the LED, but common values are 1,5~1,8V. To make the LEDs work without burning them a resistor is put in series with the LED to limit the voltage that fall in the LED and the current that goes through the LED. If you put some LEDs in series, you'll have to check they don't need more voltage than you're providing and also you have to lower the resistor in series with them. If you don't do it, each LED will bright less or even they can stop emitting light.

Where are you getting the power to feed the LEDs?

HomerCIDAL · Post by **HomerCIDAL** » Mon Jun 13, 2005 2:02 am

So...correct me if I'm wrong...but you can run 5 led's with a power requirement of 3.3v in parallel? Is that possible because I am considering a mod using 4 white leds and a green led and they all require 3.3v I'd hate to think I am about to waste a lot of time on something that will not work!

doragasu · Post by **doragasu** » Mon Jun 13, 2005 3:02 pm

You can but if for example you use a 150 ohm resistor for one led, you'll have to use a 150/5 = 30 ohm resistor to feed the five leds (or five 150 ohm resistors, one in series with each LED).

rustcoal132 · Post by **rustcoal132** » Tue Jun 14, 2005 9:35 pm

it gots 1 resistor and i am runing the 4 extra leds (not including the modem one) in a parrallel. ( i think) i am running it from inside the little ground and 3.3v box... you know, the little white boxes
(3.3, 5.0, gnd, gnd, 12)

anyways, is it possible that if you run too many in paralell, is it possible that they will not have enough power to light up?

heres my schematic looks like.
i got 4 wires going from LEDs to 3.3v
then the other ends of the LEDs all connected to just 1 resistor.
the other end of the resistor is connected to the ground.

im not even sure if it is in parallel.
3.3v > 4 LEDs > 1 resistor > ground

dcmodder · Post by **dcmodder** » Tue Jun 14, 2005 10:58 pm

3.3v 5v gnd gnd gnd 12v and parallel is where you have

Code: Select all

gnd--|--|--|
     L  L  L
     E  E  E
     D  D  D
pos--|--|--|

so that if that first led burns out the others are still getting the voltage

Jaded JAaron77 · Post by **Jaded JAaron77** » Tue Jun 14, 2005 11:50 pm

a bit off topic perhaps:

I bought me a 20 pack of assorted LEDs today (intended for my computer). They have no current/voltage markings on the package, since it's an assortment, but they all seem to be about the same. ...I was testing them out first with AA batteries. At 1.5V none of them light up at all. At 3V they're pretty bright. The Green and Red ones handle it just fine, but I've burned up (literally) four Amber (Yellow) ones already. I've tried them alone and in parallel with red and green ones and still the amber ones are always burning out (if I put them in series with anything, it's not enough to light either of them) What do you think about this? I was planning on running three of them off the +5V on one of my (many) extra drive power cables (with a resistor of course.. though I've not figured up yet what value it should be). Anyone know why (only) the amber ones are burning out running off just 3V from two AA batteries?

royhubbs · Post by **royhubbs** » Tue Jun 14, 2005 11:51 pm

wheres a good place to get these led's????

Matt · Post by **Matt** » Wed Jun 15, 2005 3:17 am

lsdiodes.com

dcmodder · Post by **dcmodder** » Wed Jun 15, 2005 10:14 am

maybe they're not amber until you're over loading them and burning them out. maybe they're green. there are really low voltage leds. they're good for drive access lights because they're so sensitive.

Jaded JAaron77 · Post by **Jaded JAaron77** » Wed Jun 15, 2005 11:07 am

they're amber, they're not the ones with the clear shell, it has an amber shell. I used a variable resistor to test another one (what I should have done from the start) and found it to be best around 1.8 to 2 volts. Been playing around with it, and calculating values for resistors all morning and finally have it set up to run my red, amber, and green LEDs of the +5V and my blue off the +12 (the blue one I bought separate so it was marked 5V) from my computer (been testing it with the power supply in an external hard drive case) Haven't killed on yet today...but I've also made sure my resistors were a bit stronger than what I actually need.

...though now I've the problem of my green ones needing about .2V more than the red and amber... I guess I'll just leave it dim

...since I've got so many extra LEDs I might put some in my Dreamcast too